The proposed research is designed to investigate developing neuroanatomical changes taking place as competence within a particular learning paradigm is first being behaviorally expressed. The animal model chosen for this study is the Peking duck embryo, which has been found to exhibit a sharp behavioral discontinuity between prenatal days 23 and 24 with respect to an operant escape learning paradigm. This study will first determine the exact central nervous system areas essential to acquisition in this learning task by the discrete ablation technique. This investigation will be followed by detailed histological analyses of these critical areas, comparing a number of maturational indices between animals which are competent or pre-competent with respect to the task. These analyses will include volumetric measures and cell size determinations of Nissl stained material, analysis of details of cellular differentiation using a Golgi stain, and analysis of differential myelinization within the defined critical areas. It is hoped that these analyses will reveal maturational factors, events, or mechanisms critical to the emergence of learning capacities. This study represents the first attempt at a structure-function manipulative-correlative analysis of developing learning. It is felt that an improved understanding of the developmental factors critical to emerging learning will eventually enable us to promote, protect and nurture these crucial prerequisites, and to ultimately prevent the abnormal development of this vital capacity.